A warning was issued for residents in Durham Lead and Scotsburn, who are urged to leave their properties as a precaution.

Incident controller Gavin Hope told ABC radio the fire was 20 hectares in size and moving through grassland, "giving us some grief" in forest areas.

At least 50 firefighters are tackling the blaze with four aircraft joining the battle and bulldozers are being used to make firebreaks, he noted.

Breaking: out-of-control bushfire south of Ballarat. Emergency Warning in place for Brennans Rd and Pryors Rd, Platts Rd, Buninyong. Bushfire has crossed Scotts Lane and is heading in a southerly direction @9NewsMelb#vicfirespic.twitter.com/RnNBM9dadP